The aim of the current double-blind, placebo controlled randomized clinical trial is to study the effects of Probiotic supplement containing Lactobacillus acidophilus, LA-5 and Bifidobacterium, BB12 on weight changes, glucose metabolism and inflammatory and oxidative stress indices in women with gestational diabetes mellitus. Sixty four volunteer pregnant women, singleton primigravida, with gestational diabetes mellitus diagnosis without the history of diabetes, hypoglycemic drug usage, chronic disease, smoking, alcohol consumption and Probiotic food products consumption in current two weeks will be included in the study and in case of need for insulin or other hypoglycemic drugs, they will be excluded. All the participants will be divided into experimental and control groups using random sampling method and they will receive one Probiotic or placebo capsule along with dietary advice for eight consecutive weeks, respectively. Ten milliliter blood drawn via venous puncture will be subjected for analysis of biochemical markers including glucose metabolism indices (serum glucose and insulin, HOMA-IR and QUICKI indices), inflammatory indices (highly sensitive C- reactive protein/hs-CRP, TNF-α and Interleukin-6) and oxidative stress indices (total antioxidant capacity/TAC, malondialdehyde/MDA, superoxide dismutase/SOD, glutathione reductase/GSH-R, glutathione peroxidase/GSH-Px and uric acid). Also weight changes will be determined by digital scale before and after intervention. The data will be entered in related software and analyzed by appropriate statistical methods to study the effect of the intervention on serum levels of the selected bio-markers and weight changes.